1. Field of the Invention
The invention relates generally to the field of image processing. More specifically, the invention relates to a method and apparatus for providing lossless data compression and editing media content.
2. Description of the Related Art
Current motion picture productions generate vast amounts of film footage throughout the course of a feature's creation. Often shot on location or on elaborate sets, production of a feature is expensive, and production cost is measured by the number of production days expected. Recognizing that a production day must he fully utilized and likely not re-duplicated or re-scheduled, scenes are shot several times to ensure that the creative intent for the feature is captured. This safeguard generates a large amount of original film footage.
It has been estimated that a standard feature production has a cutting ratio of approximately 20:1. Therefore, for a typical two-hour feature presentation, approximately 40 hours of film footage is gathered, in a big budget production, it is not unreasonable to expect about one million feet of film. To be able to provide the production with the entire assets of 40 hours of film, whenever they are desired, it would be necessary to have approximately 3.45 million film frames available, 40 hours of film footage being 3.45×106 frames (40 hours×60 minutes/hour×60 seconds/minute×24 frames/second=3.45×106 frames total). Assuming that the footage data has a resolution of 2048×1742 at 10 bits (2K) and is not compressed, and has a 2.35 aspect ratio (“AR”), this amounts to approximately 12 megabytes (“MB”) of storage per frame. The footage data would therefore require about 40 terabytes (“TB”) of storage space. For 4K resolutions, the storage requirements would increase by a factor of four, thus, one million feet of film footage would require 160 TB of storage space. Over and above these large and expensive storage requirements, the asset tracking, identification, and management of this data is an extremely expensive and difficult task,
Another problem arises when it is desired to re-edit legacy television programs from original footage. Most legacy television programs, i.e., television programs from a previous time or generation, were created from film sources, and assembled using video processes. As a result, the original film footage of many legacy television shows, which typically have very high resolutions, cannot be reused to recreate the final-cut version of the television programs in a higher resolution or a different format. This is because, even though the original film footage exists, the edit lists that were used to create the final-cut version of the television program are no longer available. As a result, it cannot be determined which frames from the original film footage were used to create the final-cut version of the television programming.
Traditionally, motion pictures have been captured on film at a rate of 24 frames/second at a very high resolution (e.g., 4K resolution). Once all the original film footage has been taken and reviewed, edit lists are created, and the uncut portions of the film are typically converted to another, more usable format. For example, the original film can be transferred to video, which is shown at a rate of 60 fields/second. Due to advances in technology, viewers of television and motion pictures now expect a relatively high-resolution picture qualify. Therefore, content providers often need to provide their motion picture content in a higher resolution than it originally was created. Unfortunately, reusing the original film footage to create the edited material in a higher-resolution format is extremely difficult because the edit list that was used to create the edited material typically is not available. Without the edit list, it is a very difficult and time-consuming process to determine which film frames were used in the video program and which film frames were cut from the original video program.
Conventional processes for converting film to video have been around for many years and are well known in the art. The typical method involves converting the 24 frames/second of film to 60 fields/second of video. Through this process, four frames of a film are converted to ten video fields. This is accomplished by adding redundant frames from the film to the video fields to make up for the difference in the number of images shown per second between the two formats. Typically, this is done by taking each of the four frames from the film and alternating showing each of those frames for either two or three fields. A typical four film-frame sequence 10 is shown in FIGS. 1 and 2. Using this method, two of the film frames 12 and 14 (i.e., film frames A and C) would be shown for two video fields 16 and 18, respectively, each (four video fields 20 total) and the other two film frames 22 and 24 (i.e., film frames B and D) would be shown for three video fields 26 and 28, respectively, each (six video fields total), totaling ten fields of video that were created from the four frames of original film footage. This method is repeated for the 20 remaining frames of film in the second of footage to create 60 fields/second of video programming. As shown in FIG. 2, the video fields alternate between being a video field one 30 and a video field two 32. Each video field includes half of the scan lines, i.e., every other scan line, that are displayed on a video output device, e.g., a monitor.
Unfortunately, the process of converting film 34 to video 36 described above results in some of the frames 12 and 14 of the film being shown for two video fields 16 and 18, respectively, while other frames 22 and 24 of the film are shown for three video fields 26 and 28, respectively. Showing some film frames for a longer period of time than others results in a staggered timeline having undesirable motion artifacts in the video program. These artifacts are not acceptable by today's standards. Additionally, video content typically is delivered on optical disc, e.g., digital video disc (“DVD”), or transmitted using a data transmission line or related method, e.g., Video on Demand (“VOD”). As a result content providers want to provide as much high-resolution content on a DVD or within the available bandwidth of the data transmission line. Space on a DVD or bandwidth of a data transmission line cannot be wasted. Therefore, it is no longer acceptable to provide video content that contains redundant fields from the original film frames.
Additionally, many difficulties exist with trying to extract the original frames 12 from a video source 36 that contains redundant images. For example, the practice of varying the speed of the film material 34 when creating a video program makes it difficult to identify and remove the original film frames of the film source. In a variable-speed process, the film is not run at the typical 24 frames/second, but rather at a subtly faster or slower speed to shorten or lengthen the resulting video program. This is typically done either to accommodate commercial breaks in the video program, or to vary the pace of the video program on a scene-by-scene basis. As a result a video program that results from the variable-speed process does not contain the 2:3 field sequence (or 3:2 field sequence) described above. Instead, the speeding up or slowing down of the film frames through the variable-speed process results in a seemingly random sequence of two and three video fields 16 and 26, respectively. For example, to lengthen a 24 film frame scene from the 60 video fields it would normally be, to a new length of 66 video fields, the sequence might be 3,2,3,3,3,3,2,3,3,3,3,2,3,2,3,3,3,3,2,3,3,3,3,2 (“the first sequence”), or it could be 3,3,3,3,3,3,2,3,2,3,3,2,3,3,3,3,3,3,2,3,2,3,3,2 (“the second sequence”). These two sequences are virtually indistinguishable to the viewer. To further complicate matters, no standards have ever existed for modifying the 2:3 field sequence (or 3:2 field sequence) using the variable-speed process, in fact, the same variable-speed device can create the first sequence referenced above, and then, immediately afterwards, create the second sequence referenced above, when varying the speed of the same film material.
Another problem that is associated with determining the original film frames 12 in the previously discussed 2:3 (or 3:2) sequence is caused by various post-production practices. Most notably, the post-production practices of fixed-field dominance, i,e., the starting of every new shot on either video field one 30 or video field two 32, and video-switcher effects create additional problems with identifying the original film frames in the resulting video program 36. In the past, video editors could edit video field one or video field two, but lacked the precision to reliably edit on all the video fields 20 that required editing. Typically, video editors would make all of their edits on video field one. However, as shown in FIG. 1, only two film frames 12 and 14 of the four film-frame sequence 10 started on video field one. The other two film frames 22 and 24 start on video field two. The same is true on the out points or last field of edits. Assuming you have a section of film having four film frames A-D, like the frames shown in FIG. 1 if the video editor makes a field one dominant edit on an “A” frame 12 or a “B” frame 22 then no problem arises, however, if the dominant edit is on a “C” frame 14, then an orphaned video field is produced with only half of the vertical resolution. The orphaned video field has only half the resolution because only one video field of a given image is available, if the film frame that you are editing to is a “D” frame 24, then you have shortened three video fields to two video fields since the “D” frame starts on video field two, effectively converting a “D” frame to an “A” frame. This can result in temporal discontinuity, which results in a bump or jerk in the motion of a scene with a lot of movement in the resulting video program.
Similarly, video-switcher effects, such as dissolves or fades to black, create additional problems with identifying original film frames 12 included in the video program 36. These video-switcher effects were commonly done using 60-field video switchers. One can appreciate that in a 60 fields/second fade to black, every video field 20 is unique. As a result, determining which two or three video fields comprise a unique film frame becomes difficult and complicated.
Accordingly, it should be appreciated that there is a need for a method and an apparatus that provides lossless data compression of large amounts of film footage 10 and accurately determines and separates unique film frames 12 from video 36. The present invention satisfies these needs and provides other related advantages.